1. Field of the Invention
The present invention relates to a life diagnosis apparatus for determining and indicating the service life of an automotive battery, or more in particular to a life diagnosis apparatus for automotive battery capable of diagnosing the charged condition and the service life of an automotive battery with improved accuracy.
2. Description of the Prior Art
In conventional life diagnosis apparatuses for automotive battery as disclosed in JP-A-No. 53-79238, JP-A-No. 53-127646 and JP-A-No. 56-126774 specifications, the terminal voltage, charge-discharge current and the temperature of a battery for automobiles (hereinafter referred to as a "battery") are detected, and the detection values are processed by a computer to determine output values related to the charged condition and the service life of the battery including the amount of balance charge, starting amount of charge, internal resistance and the shorting current, thereby judging and diagnosing the service life and the charged condition by comparing these output values with a predetermined reference level.
These prior art apparatuses, however, do not have any means for offsetting the initial variations of the batteries, which are added, together with the error in correcting the changes in the detection conditions, to the secular variations. As a result, if an attempt is made to make simple judgement and diagnosis with a threshold value, the resulting error often causes normal products to be confused with troubled products.
Further, in the prior art described above, it is rare to detect, process, indicate and control the internal resistance and the leak current clearly, which represent the residual amount of available charges and the degeneration of the battery. As a consequence, a battery not charged in full is often disposed of as a degenerated product, or a battery whose life has expired is charged in full for use under the low-temperature environment of a cold area often resulting in a starting trouble.